Abstract-Current marine wireless communication systems used for monitoring applications based on buoys suffer from lots of weakness. Many research works concern the design and development of new technological applications to improve marine communications. Particularly, a wireless communication system based on WiMAX standard at the 5.8 GHz band (license-exempt band) could be a good candidate. As an initial task, a propagation channel measurement campaign in maritime environments was carried out to investigate the impact of the wireless channel in different situations. This work provides large scale path loss measurements over sea around urban environments. In particular, a radio link between a buoy and a ship at 5.8 GHz is studied. NLOS (Non-Line-Of-Sight) paths are investigated in depth and they are compared to LOS (Line-Of-Sight) paths. The designed measurement system is described and the experimental measurements are shown. An empirical model is obtained using these experimental data and the key wireless channel parameters are analyzed. In addition, the empirical model is compared to the free space and two-ray theoretical models. This investigation is useful, among others, for planning Worldwide Interoperability for Microwave Access (WiMAX) networks offshore around these challenge environments.Propagation channel measurements; Sea; WiMAX; urban environments;

New wireless applications are emerging subsea. Pinless Subsea Connectors (PSC) aim to transfer high-speed data over short distances. They present several advantages in comparison with previous technologies. However, its design presents several challenges that need to be addressed. For PSC based on electromagnetic signaling, one of the principal factors affecting system planning is signal attenuation. This work characterizes the impact of water temperature on signal attenuation in both freshwater and seawater. We present experimental data in the 0.5-3.5 GHz band at two typical values for the water temperature (5 and 22 °C). The study confirms that higher temperatures may help to enlarge system coverage in freshwater. However, the opposite effect is found in seawater. The obtained patterns of attenuation with the temperature are in agreement with the available empirical data. However, we also show that available data bases are not accurate enough for estimating signal attenuation for the presented working conditions.

Experimental fading measurements were performed in Cadiz Bay, Spain, for a variety of operational scenarios over the sea at the unlicensed 5.8 GHz frequency band. Measurements are based on continuous wave (CW) transmissions with both the transmitter and the receiver installed in typical low-height maritime platforms, such as oceanographic buoys, military ships and boats. Based on the measurements, large-scale and small-scale fading statistics are characterised by cumulative distribution functions (CDFs) and key wireless channel parameters are estimated and discussed. Results show, first, that large-scale fading can be modelled using classical log-normal pathloss models and, secondly, that small-scale fading statistics fits the extreme value distribution (EVD) function when they are expressed in decibel units. This study can be used for practical planning of wireless communications in maritime applications and as an experimental basis for further simulation works.

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-This work presents experimental propagation measurements over sea at 5.8 GHz for a radio link between an antenna installed aboard a boat and an antenna installed onshore. Experimental data include path loss and large-scale fading. We focus on modeling obstructed paths. Measured local mean power values show that a multi-slope path loss model are more appropriate than traditional models that use only one slope for NLOS (Non-Line-of-Sight) transmissions. The received signal was found to attenuate at the rate of up to 130 dB per decade in some shadow regions. It was also found that measurements fit reasonably well the two-ray model while LOS (Line-Of-Sight) condition remains. This investigation is useful, among others, for planning Wireless Sensor Networks offshore.